What is good self-treatment for tmj?

Common sense! Tmj problems often respond to simple conservative treatment. This includes a soft, non-chewing diet consisting of things like mashed potatoes or grits, and avoiding gum chewing. Also, many patients respond well to over the counter non-steroidal anti-inflammatory medications, like Ibuprofen or Naproxen (aleve). Another mainstay of treatment is moist heat applied to the joint.
A few things. . Self treat with soft diet, jaw exercises, massage, heat/cold, OTC pain meds. A splint or physical therapy would be next. Occasionally muscle relaxants, biofeedback. Xrays are done for diagnosis. Surgery usually reserved for serious symptoms not responsive to other treatments.
Must be careful. Self-treatment can help in some cases, but can also cause an acute issue to become chronic or permanent if care is not heeded. For example, an otc mouthpiece may see like the easy and most economical solution, but it can actually exasperate other ailments without actually helping. See a specialist first who can guide you with proper office and home care.
NSAIDS & Splints. A good combination of home treatment with nsaids and dental visits with splint therapy may optimize TMJ treatment and minimize discomfort. Of course don't take any medications without referring to your doctor. Soft diets and home physical therapy may also be advantageous. Contact your dentist for best approach.